xbleed start during push back

[graziani]

Is it possible ( with B737) start the engine n°2 with xbleed start during the push back maneuver???
if the tractor is very big and strong, is it still prohibit ???
I couldnt fing any limitation regarding it....if you do paying attention is it legal????:confused::confused:

[Meikleour]

graziani: I am sure its possible..............but the question you should be asking .....................is it WISE?

[A and C]

You would be unwise to do so, one engine at high power is enough to put a lot of extra load on the tow bar with the potential to break the shear pins in the bar.

The result of this would be the aircraft propelling its self at high assymetric power towards a tractor also at high power going in the opposite direction, who knows which way the sheared tow bar would go !

The chances of one of the ground crew going into the engine are high and it is very likely the tractor driver would be crushed between the loose aircraft and the tractor.

And all this for what ? Saving a few seconds............ As I said a very unwise and unsafe idea.

[graziani]

I know that it is a maneuver where you have to pay attention with risk.....
Im not asking if wise or not ...

But Iwoukld like to know if there is any legal doc regarding this procedure and what boeing says about it ???:hmm:

[Swedish Steve]

It is prohibited by all airlines I have worked with.
If you tried it while I was on the headset, the pushback would stop and we would be gone.
You have to advance the throttle when the aircraft is pointing in the wrong direction. There may be loose containers behind that you blow over, and you can easily break the tow bar.
Don't try it.

[TOWTEAMBASE]

Not to mention and pax boarding or disembarking in the jet blast path getting pebble dashed.as mentioned,far too dangerous, even for the biggest tug, or most experienced driver. Always straight down the taxi way, engine towards blast screen, and tug/tow bar disconnected (maybe chock in front of nose wheel) prior to over idling running engine.i suppose it does depend on airport rules though

[Denti]

On certain airports we used, it was normal SOP to do it during push back. No tow bar in use there and the tractors were rated up to A380 and had no problem at all with tiny aircraft like our 737s, enough blast space behind and no open boarding and deboarding possible anyway, only via protected jet bridges, even on non-terminal positions.

[Emel.OW]

I think if you try this and break a pin or a tug you'll be told the exact document and Boeing's opinion, but will this make you happy? ;)

[aviatorhi]

Why does there need to be a legal doc to prohibit something idiotic? Are you an airman or a drone?

[nitpicker330]

On a 737? Nope
However on the A330 or 777 no problems as you get enough bleed from the running Engine at idle. :ok:

[glum]

No problem on the Tristar either - it was normal procedure to fire up one engine prior to pushback, then fire up the second once you're rolling backwards.

If the tug is up to it, and the groundcrew briefed then there is no safety problem. Anything in the efflux path means the groundcrew won't give permission to start anyway...

[Cough]

Grazini...

Have a read of this (http://www.skybrary.aero/bookshelf/books/1018.pdf) which should answer your question.

[JeroenC]

Cool hé, some people nearly call the OP a moron, other say it's SOP in their company...

[Gerd53]

@ glum
Of course it's a normal procedure to start the engines during push back but with APU bleed air only. I remember a A321 in FRA which tried a cross bleed start during push back and this resulted in a hugh damage!

[tdracer]

About a year ago, there was a 777 that was starting an engine during pushback (using the APU). Unfortunately the crew had neglected to place the throttle to idle before initiating the start - as soon as the engine started it rapidly accelerated to power.

The aircraft rotated into the tug and the (running) engine impacted the tug. From the event report "The pushback tractor driver, during these events, run away from his position in the tractor’s cabin…" :eek:

Miraculously no serious injuries, but considerable damage to both the airplane and the tug. Presumably there was also damage to the tug drivers underwear :sad:

[grounded27]

The only person you should be asking this question to is your engineer/technician if pushing. Generally I do not clear for advancement in throttle until I have the tug and towbar linear with the aircraft close to the taxiway/lane line. All aircraft are different, I watched a 777 with 115B's snap a towbar in a tight turn during pushback with one engine running and the other cranking. If it was a 737 or 319 I might not care.

[captjns]

Is it possible to cross bleed start during push back? Sure it's possible. Is it smart? Check your NNPs in your FCOM and you will discover that it's not a smart move to do a cross bleed start during pushback.


Starting both engines with the use of the APU during pushback is not to be confused with a cross bleed start.

[A and C]

glum I am assuming that you misunderstand the B737 terminology, I don't think that you would put one of the wing engines on your Tristar up to 80% N1 during pushback.

Chough

I am endebted to for finding that accident report, I did not know of the inccident but it seems to have panned out much as I predicted in post #3 but fortunately without injury to any one, but clearly the tractor driver was of the opinion that it was wise to leave the area with some haste!

Graziani

As English is clearly not your first language I will tell you that when an Englishman says that something is unwise it is a polite way of saying that it is a stupid idea. My concern is that you are more interested in if there is an SOP for this or some legislation to prohibit the practice rather than considering the physical aspects of the way the forces that the aircraft and tractor are producing will be interacting, if you had taken the time to think about this you would have been unlikely to ask the question in the first place.

On a general note I have noticed that some of the newer people in the industry have become SOP drones who are totaly convinced that if they stay on SOP and within all the rules they will be safe, they are very keen to point even the slightest non compliance with SOP without understanding the reason. These people seem to know every thing and understand nothing.

[olster]

really not a good idea...

[Emel.OW]

On a general note I have noticed that some of the newer people in the industry have become SOP drones who are totaly convinced that if they stay on SOP and within all the rules they will be safe, they are very keen to point even the slightest non compliance with SOP without understanding the reason. These people seem to know every thing and understand nothing.

These words are worth being printed in every SOP as an afterword! Preferably in bold type :)

[Check Airman]

But Iwoukld like to know if there is any legal doc regarding this procedure and what boeing says about it ???

Actually, there is a legal document preventing it, at least in the US

eCFR ? Code of Federal Regulations (http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=dddb1dcaf28753aa8e33ad14ab1919f8&rgn=div8&view=text&node=14:2.0.1.3.10.1.4.7&idno=14)

[nitpicker330]

I wouldn't do it in any Aircraft that required above idle thrust from the running Engine in order to achieve the required duct pressure.

What I said was its ops normal in the 777 or A330 to carryout a cross bleed start during pushback because you don't need more than idle thrust to achieve required minimum duct pressure for a successful start of the other Engine.

If there is any doubt then don't do it during push, either do it before push or after depending on the Tarmac, ATC requirements and ground crew requirements etc etc.

Common sense gentleman. :ok:

[DutchOne]

What I said was its ops normal in the 777 or A330 to carryout a cross bleed start during pushback because you don't need more than idle thrust to achieve required minimum duct pressure for a successful start of the other Engine.

Definitely NOT true on the A330. Often you need to increase thrust above idle to keep the pressure sufficient. Especially in hot and/or high conditions.

[nitpicker330]

Rubbish, I've done quite a few cross bleed starts on our A330's in the last 5 years and always done it during push without needing to increase thrust. The duct pressure always stayed above the required 25 psi with the start valve open. Naturally we read and do the procedure straight from the book.

In fact the A330 FCOM Supplementary Procedures Power Plant section procedure clearly states:--

"The remaining Engine is now started by crossbleed air from the operating Engine. This may be done during pushback...."

Now if yours doesn't say that then..............

I should add that we have RR Trent Engines...

[A and C]

You are correct and there will be much the same legislation in place world wide but this requires interpretation.

The latest breed of children have been living in a culture of non responsability for their actions, as soon as an accident happens they run to their lawyers and try to blame anyone apart from themselfs, this is why they know the regulations & SOP's right down to the smallest detail because that way they think they can keep themselfs safe from the authority's. In the legislation you link to it says nothing about crossbleed starts, so in the logic of these people it is not prohibited and so not wreckless, this would be their defense in court.

The problems are that actions may be legal but they are not wise, and in some situations the wise action may not entirely be in compliance with all the rules, unfortunately with the current fashion for rushing to the court room as soon as anything goes wrong we have produced a generaton of people who only see life from a leagal point of view and use this to protect themselfs from their own stupid actions.

That is why when you buy a packet of peanuts it has a warning on the packet telling you that the product contains nuts............... It is the manufacturs protecting themselfs from those devoid of common sence but with access to a lawyer.

[DutchOne]

Hey Nitpicker330,


Interesting reply. Funny that my 5 year experience is different. Besides my manual has a different note: to increase up to 30% N1 if needed to obtain the pressure needed. We have mainly GE engines though, but a few RR Trent too.


Guess the Northern Hemisphere has adverse effects ;)

[NSEU]

We have a pushback procedure on our our aircraft which even prohibits main engine start _using APU_ if any part of the pushback involves forward movement. On some aircraft types, to facilitate easy towbar disconnection, the aircraft is towed forward in a straight line for 20 feet.

Obviously, procedures are guided by past incidents/accidents.

[fireflybob]

You are correct and there will be much the same legislation in place world wide but this requires interpretation.

The latest breed of children have been living in a culture of non responsability for their actions, as soon as an accident happens they run to their lawyers and try to blame anyone apart from themselfs, this is why they know the regulations & SOP's right down to the smallest detail because that way they think they can keep themselfs safe from the authority's. In the legislation you link to it says nothing about crossbleed starts, so in the logic of these people it is not prohibited and so not wreckless, this would be their defense in court.

The problems are that actions may be legal but they are not wise, and in some situations the wise action may not entirely be in compliance with all the rules, unfortunately with the current fashion for rushing to the court room as soon as anything goes wrong we have produced a generaton of people who only see life from a leagal point of view and use this to protect themselfs from their own stupid actions.

That is why when you buy a packet of peanuts it has a warning on the packet telling you that the product contains nuts............... It is the manufacturs protecting themselfs from those devoid of common sence but with access to a lawyer.

A & C - quite the most succinct summary of the culture we live in - thanks!

There is a big difference between "doing things right" (aka management) as opposed to "doing the right thing" (aka leadership)

[nitpicker330]

DutchOne---I can't explain the difference? My company was ( or still is ) the biggest 330 operator in the world since 1996 and we fly in both hemispheres!!

Anyway I can only tell you what we do. :ok:

[Luke SkyToddler]

Definitely need to increase thrust up to about 40% N1 (from the idle around 28-30%) on our P&W powered A330s, to get sufficient duct pressure for the crossbleed start.

Also for what it's worth, crossbleed start during the pushback is prohibited under our SOP, it's only allowed while stationary with the park brake set.

[nitpicker330]

Fair enough, I knew there was something good about the RR Trent!!